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Determining the Thermal Efficiency of a Polymer Solar Collector Using Numerical Methods

With the use of polymeric materials, such as polycarbonate or poly (methyl methacrylate), it is possible to relatively easily alter the design of the flat plate collector to achieve as high as possible values of thermal efficiency and to produce technically competitive collectors at lower costs than the state-of-the-art flat plate ones. Determination of the thermal efficiency is one of the crucial parts of the process of the design optimization. To assess the thermal efficiency of various designs of the polymer solar collector, different 2D numerical models were used. Because the design of the polymer solar collector is often more complex compared to the standard flat plate collector, the more complex numerical models may be considered, such as discrete ordinate (DO) radiation model. The developed models were first analytically and experimentally evaluated against the standard flat plate collector. Furthermore, the separate numerical models are applied to a computational domain of simplified geometry. The solar incident radiation is modeled with the ray tracing software. These models are then validated experimentally to confirm the accuracy of the ray tracing software. The most appropriate model is selected to obtain the efficiency of a polymer solar collector prototype. The results show that polymer solar collector has 3.45% lower efficiency when the temperature difference between water and ambient temperate is zero. As the water temperature increases, the efficiency curve of a polymer collector has steeper characteristic than the flat plate one due to inferior thermal properties of a polycarbonate. Moreover, the developed model can be applied to various designs of solar collectors made of different materials to evaluate the thermal performances.

Solar energy ; polymer solar collector ; flat plate collector ; radiation modeling ; heat transfer analysis ; renewable energy

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